Danr, you will probably get more response if you start a new thread on the subject of
oil additives.
By the way I add one of these every other
oil change: Pro Blend No. 8080 Racing Formula
http://www.pro-blend.com/ENGINELUBE2.htm
Here it is on Amazon:
http://www.amazon.com/Pro-Blend-8080.../dp/B0002W09MA
Keeps engine cool.
AZ Bob